Abstract
Background: Maintaining a therapeutic range of International Normalized Ratio (INR) in patients with mechanical prosthetic heart valves is of paramount importance. The effect of religious Fasting and altered lifestyle pattern during the Holy month of Ramadan on the INR stability has not been previously studied in the Saudi population.
Objectives: We aimed to evaluate the effect of Ramadan fasting on the INR stability in patients using warfarin anticoagulation for mechanical prosthetic heart valves.
Design: Data were extracted retrospectively from a specialized anticoagulation clinic electronic database and were anlysed in a case-control manner, where Ramadan INR of each study subject was compared to his/her own pre-Ramadan INR level.
Setting: Prosthetic Valve Anticoagulation Clinic at King Abdul-Aziz Cardiac Center, Riyadh.
Materials and methods: Using Point-Of-Care (POC) testing, the first INR level during Ramadan as compared to the average baseline INR readings over the last 3 months before Ramadan. The study was conducted between July 29th and August 20th, 2015, which corresponds to the month of Ramadan, 1436 Hejra Calendar. Several exclusion criteria were applied to minimize the effects of potential confounding factors.
Main Outcome measures: Paired t-test was used to detect any statistically significant difference in the INR level between Ramadan and pre-Ramadan readings, in the overall study cohort and among pre-specified study subgroups.
Results: One-hundred and fourteen (114) consecutive patients fulfilled the inclusion criteria. Mean age was 48.4±13.6 years and males constituted 58% of cases. Low target (INR: 2.0-3.0) and high target (INR: 2.5-3.5) therapeutic ranges represented 35% and 65% respectively. Mean INR level was 2.81 at baseline and 2.75 during Ramadan with no statistically significant difference between them (P=NS). Achieving the desired target INR level before Ramadan was feasible in 62.5% and 64.8% of the low and high INR target groups respectively. However, maintaining the desired INR level during Ramadan was feasible in 67.5% and 51.3% of the low and high target INR groups respectively (P= 0.07). Duration of anticoagulation, warfarin dose, and adherence scale did not contribute significantly to the primary outcome.
Conclusion: Ramadan fasting and its associated lifestyle changes in the Saudi community may aggravate the INR fluctuations in warfarin-treated patients. During Ramadan, warfarin-treated patients are more prone to develop supra-therapeutic INR and therefore they deserve careful attention and closer INR monitoring.

Key words: Anticoagulation, INR, Ramadan, Fasting, Mechanical Heart Valves